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2. If the picture " tears out" when the receiver is jarred
it may be due to microphonic 6AB7/1853, 6AC7/1852 or
6J5 tubes.
3. The 6J5 oscillator tube should be removed without
rocking it in its socket to loosen it, as the rocking motion
may cause the 80.5 mmf capacitor to break off.
4. The coils in oscillator circuit should not be touched or
moved or the alignment of the receiver will be disturbed.
T he following precautions should be observed when any
work is being done on the SPU:
1. Remove power supply cord from the power supply
socket.
2. No attempt should ever be made to measure the high
(7,500 volts) voltage because of the difficulties and dangers
involved. Servicing should be done with an ohm meter.
3. If, at any time it becames necessary to service the
SPU, the suspected parts should be replaced by parts known
to be in good operating condition.
T he finest television receiver built may be said to be only
as good as the antenna design and installation. It is therefore
important to use a correctly designed antenna, and.use care
in its installation.
In most cases, the antenna should not be installed per'
manently on the apartment or residence roof until the quality
of the picture reception has been observed on a Television
receiver. A temporary transmission line can be run between
receiver and the antenna allowing sufficient slack to permit
moving the antenna. Then, with a telephone system cori'
necting an observer at the receiver and an assistant on the
roof to find an antenna location, the antenna can be posi'
tioned to give the most satisfactory results on the received
signal. A shift of only* a few feet in antenna position or di'
rection may effect a tremendous difference in picture re'
ceptfon.
W henever possible, the antenna location should be chosen
or erected so.the antenna is not only broadside to the trans'
mitter but removed as far as possible from highways, hos-
pitals and doctors' offices and similar sources of interference.
Auto ignition and diathermy apparatus may cause noise in'
terference spoiling the picture.
In mounting any antenna, care must be taken to keep the
antenna rods or pickup wires proper at least ł/» wave length
(at least 6 feet) away from other antennas, metal roofs and
Television Socket Power Units
Antenna Installation
Figure 7—R.F.— Oscillator Unit Wiring and Adjustments
TRK9, TRK90, TRKI2, TRKI20
5. The insulator on the filter capacitors may become dirty
and break down to short out the high voltage.
6. The Video coupling capacitors C50, 53, 59 should be
kept clear of chassis.
7. A gassy 2V3'G tube may cause resistor R'137 to burn.
Replace 2V3'G tube, and resistor, if necessary.
8. Changing the position of the oscillator shield plate will
disturb the alignment.
4. Use only one hand at a time. It is advisable to keep
the other hand in one's pocket.
5. Connect a shorting lead between ground (first) and
the high voltage side of O-113 and CM 14 (C-121 and CM 22
in 50 cycle models).
6. W henever working with the oihfilled capacitors, keep
a constant short across the capacitor, as these capacitors do
not completely lose their charge after being discharged a
single or several subsequent times.
7. Only one person at a time should work on the unit to
prevent any misunderstanding which may result in an accident.
gutters or metal objects. Under certain extremely unusual
conditions, it may be possible to rotate or position the an'
tenna so it receives the cleanest picture over a reflected path.
If such is the case, the antenna should be so positioned.
However, such a position may give variable results as the
nature of reflecting surfaces may vary with weather condi'
tions, as a wet surface has been known to have different re'
fleeting characteristics than a dry surface.
In short, a television receiving antenna and its installation
must conform to much higher standards than an antenna for
reception of International Short Wave and Standard Broad'
cast signals because:
(1) Intervening obstacles have a pronounced shielding
effect on the ultra'high frequency waves producing low
intensity signals. Severe trouble with multi'path transmissions
may be experienced, especially in congested city areas.
(2) The picture signal is comprised of a very wide band
or range of frequencies, all of which must be received with
good efficiency.
(3) It must be continually remembered that the discern'
ment for the eye is much more critical than that of the ear.
For further information on antennas and antenna installa'
tion see RCA Booklet entitled: " Practical Television by
RCA," and also the specific instructions accompanying the
RCA Television Antenna.
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